investigatory project on polymers for class 12 students in CBSE

Certificate This is to certify that Mr. yash Patel Student of Xll science Roll no__________ Worked on project titled-Polymer held in Bhagwati international public school during the academic year 2016-2017. He worked sincerely under the guidance of faculties and prepared this dissertation.

External Teacher Teacher

Subject

Principal

acknowledgement First of all, I am immensely indebted to almighty god for his blessing and grace without which I could not have been a success. I humbly consider a privilege and honor to express my heartiest and profound gratitude to Mr. Rajendra.S.Malwal, principal BIPS, Patan. For his appropriate direction, valuable suggestion, under judging assistance so generously extended to me. I wish to express my deepest feelings of gratitude to Mr. Nabakishor sorokhaibam, chemistry department, BIPS Patan. For his erudite involvement and sustained guidance which has been pivotal in my project work. His minute observation, precious insights, critical comments have indeed greatly helped to shape my ideas. This guidance and support received form my entire classmates who contributed and who are contributing to this project, is vital for the success of this project. I am grateful for their constant support and help. I also owe sense of gratitude to my parents for encouragement and support throughout the project.

- Yash Patel

CONTENTS 1. Polymer 2. Polymer science 3. Historical development 4. Laboratory synthesis 5. Mechanical properties

Introduction

While the term polymer in popular usage suggests "plastic", polymers comprise a large class of natural and synthetic materials with a variety of properties and purposes. Natural polymer materials such as shellac and amber have been in use for centuries. Paper is manufactured from cellulose, a naturally occurring polysaccharide found in plants. Biopolymers such as proteins and nucleic acids play important roles in biological processes. Henri Braconnot's pioneering work in derivative cellulose compounds is perhaps the earliest important work in modern polymer science. The development of vulcanization later in the nineteenth century improved the durability of the natural polymer rubber, signifying the first popularized semi-synthetic polymer. The first wholly synthetic polymer, Bakelite, was discovered in 1907. Until the 1920s, most scientists believed that polymers were clusters of small molecules (called colloids), without definite molecular weights, held together by an unknown force, a concept known as association theory. In 1922, German chemist Hermann Staudinger proposed that polymers were comprised of "macromolecules" consisted of long chains of atoms held together by covalent bonds. Though poorly received at first, experimental work by Wallace Carothers,Herman Mark, and others provided further evidence for Staudinger's theory. By the mid-1930s, the macromolecular theory of polymer structure was widely accepted. For this and other work in the field, Staudinger was ultimately awarded the Nobel Prize. In the intervening century, synthetic polymer materials such as Nylon, polyethylene, Teflon, andsilicone have formed the basis for a burgeoning polymer industry. Synthetic polymers today find application in nearly every industry and area of life. Polymers are used in the fabrication of microprocessors,

Polymer Appearance of real linear polymer chains as recorded using an atomic force microscope on surface under liquid medium. Chain contour length for this polymer is ~204 nm; thickness is ~0.4 nm. A polymer is a large molecule (macromolecule) composed of repeating structural units. These subunits are typically connected by covalentchemical bonds. Although the term polymer is sometimes taken to refer to plastics, it actually encompasses a large class of natural and synthetic materials with a wide variety of properties. Because of the extraordinary range of properties of polymeric materials, they play an essential and ubiquitous role in everyday life. This role ranges from familiar synthetic plastics and elastomers to natural biopolymers such as nucleic acids and proteins that are essential for life. Natural polymeric materials such as shellac, amber, and natural rubber have been used for centuries. A variety of other natural polymers exist, such as cellulose, which is the main constituent of wood and paper. The list of synthetic polymers includes synthetic rubber, Bakelite, neoprene, nylon, PVC, polystyrene, polyethylene, polypropylene, polyacrylonitrile, PVB, silicone, and many more. Most commonly, the continuously linked backbone of a polymer used for the preparation of plastics consists mainly of carbon atoms. A simple example is polyethylene, whose repeating unit is based on ethylenemonomer. However, other structures do exist; for example, elements such as silicon form familiar materials such as silicones

Polymer science Most polymer research may be categorized as polymer science, a sub-discipline of materials science which

includes researchers in chemistry (especially organic chemistry), physics, and engineering. The field of polymer science includes both experimental and theoretical research. The IUPAC recommends that polymer science be roughly divided into two subdisciplines: polymer chemistry (or macromolecular chemistry) and polymer physics. In practice the distinction between the two is rarely clearcut. The study of biological polymers, their structure, function, and method of synthesis is generally the purview of biology, biochemistry, and biophysics. These disciplines share some of the terminology familiar to polymer science, especially when describing the synthesis of biopolymers such as DNA or polysaccharides. However, usage differences persist, such as the practice of using the term macromolecule to describe large non-polymer molecules and complexes of multiple molecular components, such as hemoglobin. Substances with distinct biological function are rarely described in the terminology of polymer science. For example, a protein is rarely referred to as a copolymer

Historical development Starting in 1811, Henri Braconnot did pioneering work in derivative cellulose compounds, perhaps the earliest important work in polymer science. The development of vulcanization later in the nineteenth century improved the durability of the natural polymer rubber, signifying the first popularized semi-synthetic polymer. In 1907, Leo Baekeland created the first completely synthetic polymer, Bakelite, by reacting phenol and formaldehyde at precisely controlled temperature and pressure. Bakelite was then publicly introduced in 1909.

Despite significant advances in synthesis and characterization of polymers, a correct understanding of polymer molecular structure did not emerge until the 1920s. Before then, scientists believed that polymers were clusters of small molecules (called colloids), without definite molecular weights, held together by an unknown force, a concept known as association theory. In 1922, Hermann Staudinger proposed that polymers consisted of long chains of atoms held together by covalent bonds, an idea which did not gain wide acceptance for over a decade and for which Staudinger was ultimately awarded the Nobel Prize. Work by Wallace Carothers in the 1920s also demonstrated that polymers could be synthesized rationally from their constituent monomers. An important contribution to synthetic polymer science was made by the Italian chemist Giulio Natta and the German chemist Karl Ziegler, who won the Nobel Prize in Chemistry in 1963 for the development of the Ziegler-Natta catalyst.

Laboratory synthesis Laboratory synthetic methods are generally divided into two categories, step-growth polymerization and chain-growth polymerization. The essential difference between the two is that in chain growth polymerization, monomers are added to the chain one at a time only, whereas in step-growth polymerization chains of monomers may combine with one another directly. However, some newer methods such as plasma polymerization do not fit neatly into either category. Synthetic polymerization reactions may be carried out with or without a catalyst. Laboratory synthesis of biopolymers, especially of proteins, is an area of intensive research. Biological synthesis

Microstructure of part of a DNA double helixbiopolymer Main article: Biopolymer There are three main classes of biopolymers: polysaccharides, polypeptides, and polynucleotides. In living cells, they may be synthesized by enzymemediated processes, such as the formation of DNA catalyzed by DNA polymerase.

Monomer arrangement in copolymers

Monomers within a copolymer may be organized along the backbone in a variety of ways.

 Alternating copolymers possess monomer residues: [AB...]n (2).

regularly

alternating

 Periodic copolymers have monomer residue types arranged in a repeating sequence: [A nBm...] m being different from n .  Statistical copolymers have monomer residues arranged according to a known statistical rule. A statistical copolymer in which the probability of finding a particular type of monomer residue at an particular point in the chain is independent of the types of surrounding monomer residue may be referred to as a truly random copolymer (3).  Block copolymers have two or more homopolymer subunits linked by covalent bonds (4). Polymers with two or three blocks of two distinct chemical species (e.g., A and B) are called diblock copolymers and triblock copolymers, respectively. Polymers with three blocks, each of a different chemical species (e.g., A, B, and C) are termed triblock terpolymers.

 Mechanical properties

 

 A polyethylene sample necking under tension.  The bulk properties of a polymer are those most often of end-use interest. These are the properties that dictate how the polymer actually behaves on a macroscopic scale.

 Tensile strength  The tensile strength of a material quantifies how much stress the material will endure before suffering permanent deformation. This is very important in applications that rely upon a polymer's physical strength or durability. For example, a rubber band with a higher tensile strength will hold a greater weight before snapping. In general, tensile strength increases with polymer chain length and crosslinking of polymer chains.  Young's modulus of elasticity  Young's Modulus quantifies the elasticity of the polymer. It is defined, for small strains, as the ratio of rate of change of stress to strain. Like tensile strength, this is highly relevant in polymer applications involving the physical properties of polymers, such as rubber bands. The modulus is strongly dependent on temperature.

NYLON, A Condensation Polymer Nylon was the result of research directed by Wallace Hume Carothers at du Pont. The research team was interestedin duplicating the characteristics of silk. Nylon gained rapid acceptance for use in stockings and in making parachutes. Carothers, however, was subject to bouts of depression and in 1937, shortly before du Pont placed nylon stockings on the market; Carothers committed suicide by drinking cyanide. Safety Precautions  Wear safety goggles at all times in the laboratory.  The materials in this experiment are considered toxic. They are irritants to the eyes and mucous membranes. Wear gloves and work in a well ventilated area. Materials needed

 Hexamethylenediamine (1,6-hexanediamine), 5% aqueous solutionSebacoyl chloride (or adipyl chloride), 5% solution in cyclohexane Sodium hydroxide, NaOH, 20% aqueous solution  Beaker, 50 mL

 Forceps  Stirring rod. Procedure  Pour 10 mL of Hexamethylenediamine solution into a 50 mL beaker.  Add 10 drops of 20% sodium hydroxide solution. Stir.  Carefully add 10 mL of sebacoyl chloride solution by pouring it down the wall of the tilted beaker. Two layers should be evident in the beaker and there should be an immediate.

  SODIUM POLYACRYLATE, A Copolymer

 Superabsorbants were originally developed by the United States Department of Agriculture in 1966. This material consisted of a grafted copolymer of hydrolyzed starch-polyacrylonitrile (polyacrylonitrile is commonly known asAcrilan, Orion, or Creslan). The intended use was for additives for drilling fluid in off-shore secondary oil recovery operations and as agricultural thickeners. These materials were followed by synthetic Superabsorbants that arepolyacrylic and polyacrylonitrile based. Some of these materials are capable of absorbing up to 2000 times their weight of distilled water.  When a starch-hydrolyzed polyacrylonitrile superabsorbent is mixed with glycerin or ethylene glycol, the resulting firm gel has a rubbery texture and is very strong and resilient. This material can absorb about 300 to 400 times its weight in distilled water and can “grow” many times its original size. This material was formed into various shapes and sold under names such as "Grow Creatures". The process is reversible and, on standing in air, the grow creature will shrink almost to its original size on drying. It can be grown and dried many times.  A useful application of "Super Slurper" is in the liners of Pampers and other disposable diapers. Under this application, the polymer gel can absorb up to 90 times its weight in liquid. Super-absorbent material, sold under the name "Water Grabber" or "Water Lock" is available from garden supply stores.

Polymer degradation

A plastic item with thirty years of exposure to heat and cold, brake fluid, and sunlight. Notice the discoloration, swollen dimensions, and tiny splits running through the material Polymer degradation is a change in the properties—tensile strength, color, shape, molecular weight, etc.—of a polymer or polymer-based product under the influence of one or more environmental factors, such as heat, light, chemicals and, in some cases, galvanic action. It is often due to the scission of polymer chain bonds via hydrolysis, leading to a decrease in the molecular mass of the polymer. Although such changes are frequently undesirable, in some cases, such as biodegradation and recycling, they may be intended to prevent environmental pollution. Degradation can also be useful in biomedical settings. For example, a copolymer of Polylactic acid and polyglycolic acid is employed in hydrolysable stitches that slowly degrade after they are applied to a wound.

Product failure

Chlorine attack of acetyl resin plumbing joint In a finished product, such a change is to be prevented or delayed. Failure of safety-critical polymer components can cause serious accidents, such as fire in the case of cracked and degraded polymer fuel lines. Chlorineinduced cracking of acetyl resin plumbing joints and polybutylene pipes has caused many serious floods in domestic properties, especially in the USA in the 1990s. Traces of chlorine in the water supply attacked vulnerable polymers in the plastic plumbing, a problem which occurs faster if any of the parts have been poorly extruded or injection molded. Attack of the acetyl joint occurred because of faulty molding, leading to cracking along the threads of the fitting which is a serious stress concentration.

Ozone-induced cracking in natural rubber tubing

Polymer oxidation has caused accidents involving medical devices. One of the oldest known failure modes is ozone cracking caused by chain scission when ozone gas attacks susceptible elastomers, such as natural rubber and nitrile rubber. They possess double bonds in their repeat units which are cleaved during ozonolysis. Cracks in fuel lines can penetrate the bore of the tube and cause fuel leakage. If cracking occurs in the engine compartment, electric sparks can ignite the gasoline and can cause a serious fire. Fuel lines can also be attacked by another form of degradation: hydrolysis. Nylon 6,6 is susceptible to acid hydrolysis, and in one accident, a fractured fuel line led to a spillage of diesel into the road. If diesel fuel leaks onto the road, accidents to following cars can be caused by the slippery nature of the deposit, which is like black ice.